Analytical Formulation of the Jacobian Matrix for Non-linear Calculation of the Forced Response of Turbine Blade Assemblies with Wedge Friction Dampers

A fundamental issue in turbomachinery design is the dynamical stress assessment of turbine blades. In order to reduce stress peaks in the turbine blades at engine orders corresponding to blade natural frequencies, friction dampers are employed. Blade response calculation requires the solution of a set of non-linear equations originated by the introduction of friction damping. Such a set of non-linear equations is solved using the iterative numerical Newton-Raphson method. However, calculation of the Jacobian matrix of the system using classical numerical finite difference schemes makes frequency domain solver prohibitively expensive for structures with many contact points. Large computation time results from the evaluation of partial derivatives of the non-linear equations with respect to the displacements. In this work a methodology to compute efficiently the Jacobian matrix of a dynamic system having wedge dampers is presented. It is exact and completely analytical. The proposed methods have been successfully applied to a real intermediate pressure turbine (IPT) blade under cyclic symmetry boundary conditions with underplatform wedge dampers. Its implementation showed to be very effective, and allowed to achieve relevant time savings without loss of precision

Effects of culling on badger abundance : implications for tuberculosis control

Culling is often considered as a tool for controlling wildlife diseases that can also infect people or livestock. Culling European badgers Meles meles can cause both positive and negative effects on the incidence of bovine tuberculosis (TB) in cattle. One factor likely to influence the outcome of different badger culling strategies for cattle TB is the reduction in badger population density achieved. However, this reduction is difficult to measure because badgers, being nocturnal and fossorial, are difficult to count. Here, we use indices of badger abundance to measure the population impacts of two culling strategies tested in Britain. The densities of badger setts and latrines recorded before culling were correlated with the densities of badgers captured on initial culls, suggesting that both were indices of actual badger abundance. Widespread 'proactive' culling was associated with a 73% reduction in the density of badger latrines, a 69% reduction in the density of active burrows and a 73% reduction in the density of road killed badgers. This population reduction was achieved by a coordinated effort entailing widespread and repeated trapping over several years. However, this strategy caused only modest reductions in cattle TB incidence in culled areas and elevated incidence in neighbouring unculled areas. Localized 'reactive' culling caused a 26% reduction in latrine density, a 32% reduction in active burrow density and a 10% reduction in the density of road killed badgers, but apparently increased the incidence of cattle TB. These results indicate that the relationship between badger population reduction and TB transmission to cattle is strongly non linear, probably because culling prompts changes in badger behaviour that influence transmission rates. These findings raise serious questions about the capacity of badger culling to contribute to the control of cattle TB in Britain

EFFECTS OF JOINT PRODUCT MANAGEMENT STRATEGIES ON E.COLI 0157:H7 AND FEEDLOT PROFITS

The objective of this study was to determine the effect of Escherichia coli 0157:H7 on feedlot profits. Fecal samples from 711 feedlot pens in 73 feedlots in Nebraska, Kansas, Oklahoma, and Texas were tested for E. coli 0157:H7. Average daily gain and feed-to-gain ratios were computed for each feedlot pen, and managers from each feedlot provided information on various feedlot management practices. Cattle performance and E. coli 0157:H7 prevalence are both affected by feedlot management practices. The indirect effect of E. coli 0157:H7 on potential feedlot profits was determined by measuring the effects of management practices on E. coli 0157:H7 levels and cattle performance. Management practices that affect cattle performance were identified using ordinary least squares regressions. A negative binomial regression was used to identify management practices that affect E. coli 0157:H7 prevalence. Certain feedlot management practices were identified that have a joint impact on cattle performance and E. coli 0157:H7 prevalence. Using predatory insects to control flies, controlling for stray dogs, foxes, and coyotes in feed areas, removing manure from pens during finishing, and including tallow in the ration were management strategies associated with higher feedlot profits and lower E. coli 0157:H7 prevalence. Using mobile sprinklers for dust control and including alfalfa or sorghum hay or silage in the ration were associated with lower E. coli 0157:H7 prevalence and lower feedlot profits. Increasing days between cleaning water tanks and restricting movement of horses were associated with higher feedlot profits and higher E. coli 0157:H7 levels. Controlling for stray cats in feed areas and including liquid protein in the ration were associated with lower feedlot profits and higher E. coli 0157:H7 levels. These specific management strategies, which were not robust through a sensitivity analysis, should be interpreted with caution. The general categories of management strategies, however, were robust and consistent with past researchLivestock Production/Industries,

Sensing Sound And Space:Auditory And Visual Spatial ImpressionIn Three Auditoria

In some contexts, the experience of sound and space are often considered as two unrelated experiences. In an auditorium, the senses of hearing and seeing are not necessary unrelated. This thesis proposes that there is a sensorial relationship between sound and space in the context of symphonic concert halls. Through a study of three auditoria, this thesis explores the relationship, and the degree of correspondence and interaction between auditory and visual spatial impression. It begins by exploring the concepts of auditory and visual spatial impression in relation with auditorium acoustics and architectural design. In auditorium acoustics, a number of terms are used to describe auditory spatial impression, such as 'spaciousness,' 'envelopment,' and 'intimacy.' These terms have connotations beyond the auditory. The thesis suggests that they may also be used to describe visual spatial impression in auditoria. Through textual analyses, the thesis finds that the auditory and visual terms do not always relate to the same physical characteristics of auditoria and can conflict with one another. Hence, it is apparent that further subjective analyses of auditory and spatial impression are needed. Three chapters in this thesis are devoted to auditory and visual subjective experiments. Their purpose is to explore the degree of correspondence or contrast, and interaction between auditory and visual spatial impression. The degree of correspondence and contrast between auditory and visual spatial impression appear to vary between auditoria and within auditoria. The relationship between auditory and visual spatial impression appear to be both necessary and arbitrary, and the degree of interaction between them appear to be strong in some cases and weak in other. From the findings, this thesis suggests that the degree of correspondence or contrast, and interaction between auditory and visual spatial impression could be used to create an audiovisual experience that suit specific musical events. Concert auditoria are culturally and artistically unique spaces. Hence, consideration must be taken to understand the relationships between, and intentions of the acoustical and architectural designs, music and architecture, for a successful and creative collaboration between designers - since the ultimate goal is to create an extraordinary audiovisual experience in a concert hall

Plasmon excitation by charged particles interacting with metal surfaces

Recent experiments (R. A. Baragiola and C. A. Dukes, Phys. Rev. Lett. {\bf 76}, 2547 (1996)) with slow ions incident at grazing angle on metal surfaces have shown that bulk plasmons are excited under conditions where the ions do not penetrate the surface, contrary to the usual statement that probes exterior to an electron gas do not couple to the bulk plasmon. We here use the quantized hydrodynamic model of the bounded electron gas to derive an explicit expression for the probability of bulk plasmon excitation by external charged particles moving parallel to the surface. Our results indicate that for each ${\bf q}$ (the surface plasmon wave vector) there exists a continuum of bulk plasmon excitations, which we also observe within the semi-classical infinite-barrier (SCIB) model of the surface.Comment: 4 pages, 3 figures, o appear in Phys. Lett.

Structured illumination microscopy using micro-pixellated light-emitting diodes

Structured illumination is a flexible and economical method of obtaining optical sectioning in wide-field microscopy [1]. In this technique the illumination system is modified to project a single-spatial frequency grid pattern onto the sample [2, 3]. The pattern can only be resolved in the focal plane and by recording images for different transverse grid positions (or phases) an image of the in-focus parts of the object can be calculated. Light emitting diodes (LEDs) are becoming increasingly popular for lighting and illumination systems due to their low cost, small dimensions, low coherence, uniform illumination, high efficiency and long lifetime. These properties, together with recent developments in high brightness, ultraviolet operation and microstructured emitter design offer great potential for LEDs as light sources for microscopy. In this paper we demonstrate a novel structured illumination microscope using a blue micro-structured light emitting diode as the illumination source. The system is potentially very compact and has no-moving-parts

Spatial Analysis of Yield Monitor Data: Case Studies of On-farm Trials and Farm Management Decision-making

A 3-year case study was undertaken of how North American farmers use yield monitors for on-farm trials in farm management decision making. Case study methods were used because relatively few farmers quantitatively analyze yield monitor data. At this early research stage, insufficient farm management information about the data was available to ask the right questions in a large-scale survey. In addition to the formal case study of farmers experienced at using yield monitors to collect on-farm trial data, the study evaluated the effect of yield monitor data quality on farm decisions. Two levels of yield data quality included standard output where the default settings of farm-level mapping software were accepted and where filtering of the data was undertaken. Results indicated that yield data quality affects farm management decisions. In addition, farmers receiving a spatial analysis of their on-farm trial data tended to use split-field designs instead of replicated split-planter designs. They were also more confident in their decisions than before participation in the spatial analysis project, and made decisions more quickly. © 2008 Springer Science+Business Media, LLC

Modeling local terrain attributes in landscape-scale site-specific data using spatially lagged independent variable via cross regression

Analysis methods for landscape-scale site-specific agricultural datasets have been adapted from a wide range of quantitative disciplines. Due to spatial effects expected at landscape scales with respect to yield affecting factors, inference from aspatial analyses may lead to inefficient statistical inference. When spatial correlation exists within a random variable e.g. explanatory variables such as elevation or soil characteristics, spatial statistical methods can provide unbiased and efficient estimates on which to base economic analyses and farm management decisions. Simple continuous terrain variables derived from spatially lagged independent variable transformation of relative terrain position allowed models to be estimated using familiar linear aspatial models without introducing the problems associated with interpolated data in inferential spatial statistics. Using site-specific data from three example fields, cross regressive elevation variables complemented topographic attributes, rather than replacing them in a range of statistical models. Results indicated that cross regressive elevation variables, especially relative elevation, reduced estimation problems due to correlation among independent variables and bias arising from spatially interpolated data in statistical analysis

Water in the Earth's mantle: A solid-state NMR study of hydrous wadsleyite

Wadsleyite, β-(Mg,Fe)2SiO4, is the main component of the transition zone in the Earth's mantle, at depths of 410-530 km below the surface. This mineral has received considerable interest as a potential reservoir for the vast amount of hydrogen, as hydro

New Insight into Li+Dynamics in Lithium Bimetal Phosphate

Substitution of iron by other transition metals within the remarkably stable olivine framework is of interest considering the expected gain in energy density. However, manganese rich olivine materials suffer from sluggish redox kinetics, leading to electrochemical performances at high current densities which are below expectations. The source of the kinetic limitations is not clear, with multiple processes having been proposed, including low bulk electronic conductivity, structural instability of Mn3+ and a phase transition mechanism. This study employed 7Li MAS NMR relaxation techniques to indirectly probe Li+ dynamics using various stoichiometry of chemically prepared Li x MnyFe1-yPO4 (0 ≤ (x, y) ≤ 1). Focusing on the particle level, the aim was to understand how the different crystal phases, alongside the Mn structural contribution, influence Li+ transport at each stage of the oxidation process. Significantly, the formation of an olivine solid solution with vacancies within this progression gave rise to a faster 7Li transverse relaxation derived from superior Li+ motion